The prior art snap-hooks are ring-shaped and usually made from a metallic tube or rod with a circular section which is bent usually in a non circular plane to form an almost closed ring. They are provided with a closing finger which pivots at one of its ends upon the another end of the ring and turns into the plane of this ring. When the snap-hook is shut, this finger joins the ends of the ring according to a continuous closed loop which retains the inserted rope. These snap-hooks may be provided with a single or a double lock device usually mounted upon this finger and which co-operate with the body of the ring and prevents the opening of the snap-hook without the assent of the user. Such snap-hooks have a high tensile strength along their length and a less tensile strength along their width. The above mentioned lock device avoids untimely openings of the snap-hook and moreover increases its tensile strength along its width when this is a single lock device--with only one collar which slides along the finger--and still more if this is a double lock device--with two collars which slide along the finger.
All the snap-hooks of the prior art have a tilting finger which pivots into the plane of the ring and around an axis which is perpendicular to this plane of the ring. When the snap-hook is shut, the ends of the finger are in contact with the ends of the ring. When the snap-hook is open, the finger is inclined into the plane of the ring, within the inner area of the snap-hook and then the free end of the finger strikes against the opposite main longitudinal back arm of the ring, which limits the maximum tilting of the finger and the opening of the snap-hook. For achieving the adequate opening of the snap-hook which allows insertion of ropes or the like, such snap-hooks of the prior art have to be over-sized. As a result, their weight and their cost are increased more than desirable.